SiCOH dielectric material with improved toughness and improved Si-C bonding, semiconductor device containing the same, and method to make the same

ABSTRACT

A low-k dielectric material with increased cohesive strength for use in electronic structures including interconnect and sensing structures is provided that includes atoms of Si, C, O, and H in which a fraction of the C atoms are bonded as Si—CH 3  functional groups, and another fraction of the C atoms are bonded as Si—R—Si, wherein R is phenyl, —[CH 2 ] n — where n is greater than or equal to 1, HC═CH, C═CH 2 , C≡C or a [S] n  linkage, where n is a defined above.

RELATED APPLICATIONS

The present application is a continuation-in-part application of U.S.Ser. No. 11/040,778, filed Jan. 21, 2005, which application is relatedto co-assigned U.S. Pat. Nos. 6,147,009, 6,312,793, 6,441,491,6,437,443, 6,541,398, 6,479,110 B2, and 6,497,963, the contents of whichare incorporated herein by reference. The present application is alsorelated to co-pending and co-assigned U.S. patent application Ser. Nos.10/174,749, filed Jun. 19, 2002, 10/340,000, filed Jan. 23, 2003 and10/390,801, filed Mar. 18, 2003, the entire contents of each of theaforementioned U.S. patent applications are also incorporated herein byreference.

FIELD OF THE INVENTION

The present invention generally relates to a class of dielectricmaterials comprising Si, C, O and H atoms (SiCOH) that have a lowdielectric constant (k), and methods for fabricating films of thesematerials and electronic devices containing such films. Such materialsare also called C doped oxide (CDO) or organosilicate glass (OSG). Thematerial of the present invention exhibits improved cohesive strength(or equivalently, improved fracture toughness or reduced brittleness),and increased resistance to water degradation of properties such asstress-corrosion cracking, Cu ingress, and other critical properties.The present invention includes methods to make the inventive material,and relates to the use of said dielectric material as an intralevel orinterlevel dielectric film, a dielectric cap or a hard mask/polish stopin back end of the line (BEOL) interconnect structures on ultra-largescale integrated (ULSI) circuits and related electronic structures. Thepresent invention also relates to the use of the inventive dielectricmaterial in an electronic device containing at least two conductors oran electronic sensing structure.

BACKGROUND OF THE INVENTION

The continuous shrinking in dimensions of electronic devices utilized inULSI circuits in recent years has resulted in increasing the resistanceof the BEOL metallization as well as increasing the capacitance of theintralayer and interlayer dielectric. This combined effect increasessignal delays in ULSI electronic devices. In order to improve theswitching performance of future ULSI circuits, low dielectric constant(k) insulators and particularly those with k significantly lower thansilicon oxide are needed to reduce the capacitances.

Most of the fabrication steps of very-large-scale-integration (“VLSI”)and ULSI chips are carried out by plasma enhanced chemical or physicalvapor deposition techniques. The ability to fabricate a low k materialby a plasma enhanced chemical vapor deposition (PECVD) technique usingpreviously installed and available processing equipment will thussimplify its integration in the manufacturing process, reducemanufacturing cost, and create less hazardous waste. U.S. Pat. Nos.6,147,009 and 6,497,963 assigned to the common assignee of the presentinvention, which are incorporated herein by reference in their entirety,describe a low dielectric constant material consisting of elements ofSi, C, O and H atoms having a dielectric constant not more than 3.6 andwhich exhibits very low crack propagation velocities.

U.S. Pat. Nos. 6,312,793, 6,441,491 and 6,479,110 B2, assigned to thecommon assignee of the present invention and incorporated herein byreference in their entirety, describe a multiphase low k dielectricmaterial that consists of a matrix composed of elements of Si, C, O andH atoms, a phase composed mainly of C and H and having a dielectricconstant of not more than 3.2.

Ultra low k dielectric materials having a dielectric constant of lessthan 2.7 (and preferably less than 2.3) are also known in the art. Keyproblems with prior art ultra low k SiCOH films include, for example:(a) they are brittle (i.e., low cohesive strength, low elongation tobreak, low fracture toughness); (b) liquid water and water vapor reducethe cohesive strength of the material even further. A plot of thecohesive strength, CS vs. pressure of water, P_(H2O) or % humidity,which is referred as a “CS humidity plot”, has a characteristic slopefor each k value and material; (c) they tend to possess a tensile stressin combination with low fracture toughness, and hence can tend to crackwhen in contact with water when the film is above some criticalthickness; (d) they can absorb water and other process chemicals whenporous, which in turn can lead to enhanced Cu electrochemical corrosionunder electric fields, and ingress into the porous dielectric leading toelectrical leakage and high conductivity between conductors; and (e)when C is bound as Si—CH₃ groups, prior art SiCOH dielectrics readilyreact with resist strip plasmas, CMP processes, and other integrationprocesses, causing the SiCOH dielectric to be “damaged” resulting in amore hydrophilic surface layer.

For example, the silicate and organosilicate glasses tend to fall on auniversal curve of cohesive strength vs. dielectric constant as shown inFIG. 1. This figure includes conventional oxides (point A), conventionalSiCOH dielectrics (point B), conventional k=2.6 SiCOH dielectrics (pointC), and conventional CVD ultra low k dielectrics with k about 2.2 (pointD). The fact that both quantities are predominantly determined by thevolume density of Si—O bonds explains the proportional variation betweenthem. It also suggests that OSG materials with ultra low dielectricconstants (e.g., k<2.4) are fundamentally limited to having cohesivestrengths about 3 J/m² or less in a totally dry environment. Cohesivestrength is further reduced as the humidity increases.

Another problem with prior art SiCOH films is that their strength tendsto be degraded by H₂O. The effects of H₂O degradation on prior art SiCOHfilms can be measured using a 4-point bend technique as described, forexample, in M. W. Lane, X. H. Liu, T. M. Shaw, “Environmental Effects onCracking and Delamination of Dielectric Films”, IEEE Transactions onDevice and Materials Reliability, 4, 2004, pp. 142-147. FIG. 2A is takenfrom this reference, and is a plot illustrating the effects that H₂O hason the strength of a typical SiCOH film having a dielectric constant, kof about 2.9. The data are measured by the 4-point bend technique in achamber in which the pressure of water (P_(H2O)) is controlled andchanged. Specifically, FIG. 2A shows the cohesive strength plotted vs.natural log (1n) of the H₂O pressure in the controlled chamber. Theslope of this plot is approximately −1 in the units used. Increasing thepressure of H₂O decreases the cohesive strength. The region above theline in FIG. 2A, which is shaded, represents an area of cohesivestrength that is difficult to achieve with prior art SiCOH dielectrics.

FIG. 2B is also taken from the M. W. Lane reference cited above, and issimilar to FIG. 2A. Specifically, FIG. 2B is a plot of the cohesivestrength of another SiCOH film measured using the same procedure as FIG.2A. The prior art SiCOH film has a dielectric constant of 2.6 and theslope of this plot is about −0.66 in the units used. The region abovethe line in FIG. 2B, which is shaded, represents an area of cohesivestrength that is difficult to achieve with prior art SiCOH dielectrics.

It is known that Si—C bonds are less polar than Si—O bonds. Further, itis known that organic polymer dielectrics have a fracture toughnesshigher than organosilicate glasses and are not prone to stress corrosioncracking (as are the Si—O based dielectrics). This suggests that theaddition of more organic polymer content and more Si—C bonds to SiCOHdielectrics can decrease the effects of water degradation describedabove and increase the nonlinear energy dissipation mechanisms such asplasticity. Addition of more organic polymer content to SiCOH will leadto a dielectric with increased fracture toughness and decreasedenvironmental sensitivity.

It is known in other fields that mechanical properties of somematerials, for example, organic elastomers, can be improved by certaincrosslinking reactions involving added chemical species to induce andform crosslinked chemical bonds. This can increase the elastic modulus,glass transition temperature, and cohesive strength of the material, aswell as, in some cases, the resistance to oxidation, resistance to wateruptake, and related degradations. These crosslinked bonds can be folded,such that under tensile stress they can support some amount ofelongation of the molecular backbone without breaking, effectivelyincreasing the fracture toughness of the material. One most famousexample is the “vulcanization” of natural and synthetic rubber by theaddition of sulfur or peroxide and curing, as invented by CharlesGoodyear and independently by Thomas Hancock. When sulfur or peroxideare added to gum rubber, often with an aniline or other acceleratoragent, and then the material is cured under heat and pressure, thesulfur forms folded or slanted polymer crosslinks between the polymerstrands, binding them together elastically. The result is a greatlystrengthened material with increased cohesive strength, and highresistance to moisture and other chemistries. Vulcanization hasessentially enabled the ubiquitous use of rubber in many worldwideapplications and industries.

In view of the above drawbacks with prior art low and ultra low k SiCOHdielectrics, there exists a need for developing a class of SiCOHdielectrics, both porous and dense, having a dielectric constant valueof about 3.2 or less with a significantly increased cohesive strengthvs. k curve that lies above the universal curve defined in FIG. 1. Forthe particular case in FIG. 1, the fracture toughness and the cohesivestrength are equivalent. There further exists a need for developing aclass of SiCOH dielectrics, both porous and dense, with specific formsof C bonding, possibly including Si—S, S—S and S—CH bonding, withgreater organic character, increased resistance to water, particularlywithin the shaded regions of FIGS. 2A and 2B, and favorable mechanicalproperties that allow for such films to be used in new applications inULSI devices.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a low or ultra low kdielectric constant material comprising atoms of Si, C, O and H(hereinafter “SiCOH”) having a dielectric constant of not more than 3.2,and having increased cohesive strength of not less than about 6 J/m²,and preferably not less than about 7 J/m², as measured by channelcracking or a sandwiched 4 point bend fracture mechanics test.

It is yet another object of the present invention to provide a SiCOHdielectric having a covalently bonded tri-dimensional network structure,which includes C bonded as Si—CH₃ and also C bonded as Si—R—Si, whereinR is phenyl (i.e., —C₆H₄—), —[CH₂]_(n)— where n is greater than or equalto 1, HC═CH (i.e., a double bond), C═CH₂, C≡C (i.e., a triple bond), ora [S]_(n) linkage, where n is as defined above. In one preferredembodiment, the SiCOH dielectric includes Si—[CH₂]_(n)—Si wherein n is 1or 3.

It is yet another object of the present invention to provide a SiCOHdielectric material in which the fraction of C atoms bonded as Si—CH₂—Si(as detected by solid state NMR and by FTIR) is larger than in prior artSiCOH dielectrics.

It is another object of the present invention to provide a SiCOHdielectric material having a dielectric constant of not more than 3.2,which has a plot of CS vs. % humidity that shows a weak dependence onhumidity. That is, at a given dielectric constant, the SiCOH dielectricmaterials of this invention have a smaller slope than the plots shown inFIGS. 2A and 2B, and the cohesive strength at a specific value ofP_(H2O) therefore lies above the line in FIG. 2A or 2B, in the shadedregions. By “weak dependence” it is meant that the inventive SiCOHdielectrics have a lower slope in the plot than prior art materials.Within the invention, this is achieved by decreasing the number ofreactive sites (Si—O—Si). The slope of the CS vs In P_(H2O) curves isdetermined by the density of reactive Si—O—Si sites. While decreasingthe number of Si—O—Si sites decreases the sensitivity to moisture, italso decreases the cohesive strength which depends linearly on theSi—O—Si bond density. However, the dielectric material of this inventionovercomes this initial drop in cohesive strength (due to decreasedSi—O—Si bond density), by incorporating Si—C type bonding, as describedabove, which may or may not exhibit nonlinear deformation behavior thatfurther increases the mechanical strength of the material. The netresult is a dielectric with cohesive strength in a dry ambient that isat least equal, but preferably, greater than an Si—O based dielectricwith the same dielectric constant, and the inventive dielectric materialhas significantly reduced environmental sensitivity.

It is another object of the present invention to provide a SiCOHdielectric material having a dielectric constant of not more than 3.2,which is very stable towards H₂O vapor (humidity) exposure, including aresistance to crack formation in water.

It is still another object of the present invention to provide anelectronic structure incorporating the inventive SiCOH material as anintralevel and or interlevel dielectric in a BEOL wiring structure.

It is another object of the present invention to provide PECVD methodsfor depositing and appropriate methods for curing the inventive SiCOHdielectric material.

It is another object of the present invention to provide furtherelectronic structures (such as circuit boards or passive analoguedevices) in which the inventive SiCOH dielectric material is used.

In broad terms, the present invention provides a dielectric materialcomprised of Si, C, O, and H in which a fraction of the C atoms arebonded as Si—CH₃ functional groups, and another fraction of the C atomsare bonded as Si—R—Si, wherein R is phenyl (i.e., C₆H₄), —[CH₂]_(n)—where n is greater than or equal to 1, HC═CH (i.e., a double bond),C═CH₂, C≡C (i.e., a triple bond) or a [S]_(n) linkage, where n is adefined above. In accordance with the present invention, the fraction ofthe total carbon atoms in the material that is bonded as Si—R—Si istypically between 0.01 and 0.99, as determined by solid state NMR. Inone preferred embodiment, the SiCOH dielectric includes Si—[CH₂]_(n)—Siwherein n is 1 or 3.

In a first embodiment of the present invention, a stable ultra low kSiCOH dielectric material is provided that has a dielectric constant of3.0, a tensile stress of 30 MPa or less, an elastic modulus greater than15 GPa, a cohesive strength significantly greater than 6 J/m², such asfrom about 6 to about 12 J/m², a crack development velocity in water ofnot more than 1×10⁻¹⁰ m/sec for a film thickness of 3 microns, and afraction of the C atoms are bonded in the functional group Si—CH₂—Si,wherein said methylene, CH₂ carbon fraction is from about 0.05 to about0.5, as measured by C solid state NMR

In a second embodiment of the present invention, a stable ultra low kSiCOH dielectric material is provided that has a dielectric constant ofless than about 2.5, a tensile stress less than about 40 MPa, an elasticmodulus greater than about 5 GPa, a cohesive strength greater than about3 to about 6 J/m², a crack development velocity in water of not morethan 1×10⁻¹⁰ m/sec for a film thickness of 3 microns, and a fraction ofthe C atoms are bonded in the functional group Si—CH₂—Si wherein thecarbon fraction is from about to 0.05 to about 0.5, as measured by Csolid state NMR.

In alternative embodiments of the present invention, there is carbonbonded as Si—CH₃ and also carbon bonded as Si—R—Si, where R can bedifferent organic groups.

In all embodiments of the inventive material, improved C—Si bonding is afeature of the materials compared to the Si—CH₃ bonding characteristicof prior art SiCOH and pSiCOH dielectrics.

In alternative embodiments of the present invention, there may be C—S,Si—S, and optionally S—S bonding.

In addition to the aforementioned properties, the inventive dielectricmaterials of the present invention are hydrophobic with a water contactangle of greater than 70°, more preferably greater than 80°, and exhibita cohesive strength in shaded regions of FIGS. 2A and 2B. The equationfor the line shown in FIG. 2A is γ(J/m²)=−1.094 J/m²*X+10.97 J/m² whereX is 1n of P_(H2O) with P being in Pa. The equation for the line shownin FIG. 2B is γ(J/m²)=−0.662 J/m²*X+6.759 J/m² where X is 1n of P_(H2O)with P being in Pa.

The present invention also relates to electronic structures, in whichthe SiCOH dielectric material of the present invention may be used asthe interlevel or intralevel dielectric, a capping layer, and/or as ahard mask/polish-stop layer in electronic structures.

Specifically, the electronic structures of the present inventionincludes a pre-processed semiconducting substrate that has a firstregion of metal embedded in a first layer of insulating material, afirst region of conductor embedded in a second layer of insulatingmaterial, the second layer of insulating material being in intimatecontact with the first layer of insulating material, the first region ofconductor being in electrical communication with the first region ofmetal, and a second region of conductor being in electricalcommunication with the first region of conductor and being embedded in athird layer of insulating material, the third layer of insulatingmaterial being in intimate contact with the second layer of insulatingmaterial.

In the above structure, each of the insulating layers can comprise theinventive low or ultra low k SiCOH dielectric material with improved Cbonding of the present invention.

The electronic structure may further include a dielectric cap layersituated in-between the first layer of insulating material and thesecond layer of insulating material, and may further include adielectric cap layer situated in-between the second layer of insulatingmaterial and the third layer of insulating material. The electronicstructure may further include a first dielectric cap layer between thesecond layer of insulating material and the third layer of insulatingmaterial, and a second dielectric cap layer on top of the third layer ofinsulating material.

In some embodiments, the dielectric cap itself can comprise theinventive low or ultra low k SiCOH dielectric material.

The electronic structure may further include a diffusion barrier layerof a dielectric material deposited on at least one of the second andthird layer of insulating material. The electronic structure may furtherinclude a dielectric layer on top of the second layer of insulatingmaterial for use as a RIE hard mask/polish-stop layer and a dielectricdiffusion barrier layer on top of the dielectric RIE hardmask/polish-stop layer. The electronic structure may further include afirst dielectric RIE hard mask/polish-stop layer on top of the secondlayer of insulating material, a first dielectric RIE diffusion barrierlayer on top of the first dielectric polish-stop layer a seconddielectric RIE hard mask/polish-stop layer on top of the third layer ofinsulating material, and a second dielectric diffusion barrier layer ontop of the second dielectric polish-stop layer. The dielectric RIE hardmask/polish-stop layer may be comprised of the inventive SiCOHdielectric material as well.

The present invention also relates to various methods of fabricating theinventive SiCOH material.

The present invention also relates to the use of the inventive SiCOHdielectric film in other electronic structures including a structureincluding at least two conductors and an optoelectronic sensingstructure, for use in detection of light.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a universal curve of cohesive strength vs. dielectric constantshowing prior art dielectrics.

FIGS. 2A-2B show the cohesive strength plotted vs. natural log (1n) ofthe H₂O pressure in a controlled chamber for prior art SiCOHdielectrics.

FIG. 3 is a universal curve of cohesive strength vs. dielectric constantincluding prior art dielectrics as shown in FIG. 1 as well as theinventive SiCOH dielectric material.

FIG. 4A is an illustration showing preferred first precursors that canbe used in the present invention in forming the SiCOH dielectricmaterial, while FIG. 4B is an illustration showing additional CVDcarbosilane precursors that can be used.

FIG. 5 is the solid state NMR (nuclear magnetic resonance) spectra forthe ¹³C nuclei for the inventive SiCOH film A (Curve 31), for a priorart SiCOH film B (Curve 35), and for another prior art SiCOH film C(Curve 37).

FIG. 6 is an enlarged, cross-sectional view of an electronic device ofthe present invention that includes the inventive SiCOH dielectric filmas both the intralevel dielectric layer and the interlevel dielectriclayer.

FIG. 7 is an enlarged, cross-sectional view of the electronic structureof FIG. 6 having an additional diffusion barrier dielectric cap layerdeposited on top of the inventive SiCOH dielectric film.

FIG. 8 is an enlarged, cross-sectional view of the electronic structureof FIG. 7 having an additional RIE hard mask/polish-stop dielectric caplayer and a dielectric cap diffusion barrier layer deposited on top ofthe polish-stop layer.

FIG. 9 is an enlarged, cross-sectional view of the electronic structureof FIG. 8 having additional RIE hard mask/polish-stop dielectric layersdeposited on top of the SiCOH dielectric film of the present invention.

FIG. 10 is a pictorial representation (through a cross sectional view)illustrating an electronic structure including at least two conductorsand the inventive SiCOH dielectric material.

FIGS. 11A-11B are pictorial representations (through cross sectionalviews) illustrating electronic structures including a sensing elementand the inventive SiCOH dielectric material.

DETAILED DESCRIPTION OF THE INVENTION

As stated above, the present invention provides dielectric materials(porous or dense, i.e., non-porous) that comprise a matrix of ahydrogenated oxidized silicon carbon material (SiCOH) comprisingelements of Si, C, O and H in a covalently bonded tri-dimensionalnetwork and have a dielectric constant of about 3.2 or less. The term“tri-dimensional network” is used throughout the present application todenote a SiCOH dielectric material which includes silicon, carbon,oxygen and hydrogen that are interconnected and interrelated in the x,y, and z directions.

The present invention provides SiCOH dielectrics that have a covalentlybonded tri-dimensional network structure which includes C bonded asSi—CH₃ and also C bonded as Si—R—Si, wherein R is phenyl (i.e., C₆H₄),—[CH₂]_(n)— where n is greater than or equal to 1, HC═CH (i.e., a doublebond), C═CH₂, C≡C (i.e., a triple bond) or a [S]_(n) linkage, where n isa defined above. In some embodiments of the present invention, theinventive dielectric material has a fraction of the total carbon atomsthat is bonded as Si—R—Si between 0.01 and 0.99, as determined by solidstate NMR. In one preferred embodiment, the SiCOH dielectric includesSi—[CH₂]_(n)—Si wherein n is 1 or 3. In the preferred embodiment, thetotal fraction of carbon atoms ion the material that is bonded asSi—CH₂—Si is between 0.05 and 0.5, as measured by solid state NMR.

The SiCOH dielectric material of the present invention comprises betweenabout 5 and about 40, more preferably from about 10 to about 20, atomicpercent of Si; between about 5 and about 50, more preferably from about15 to about 40, atomic percent of C; between 0 and about 50, morepreferably from about 10 to about 30, atomic percent of 0; and betweenabout 10 and about 55, more preferably from about 20 to about 45, atomicpercent of H.

In some embodiments, the SiCOH dielectric material of the presentinvention may further comprise F and/or N. In yet another embodiment ofthe present invention, the SiCOH dielectric material may optionally havethe Si atoms partially substituted by Ge atoms. The amount of theseoptional elements that may be present in the inventive dielectricmaterial of the present invention is dependent on the amount ofprecursor that contains the optional elements that is used duringdeposition.

The SiCOH dielectric material of the present invention optionallycontains molecular scale voids (i.e., nanometer-sized pores) betweenabout 0.3 to about 10 nanometers in diameter, and most preferablybetween about 0.4 and about 5 nanometers in diameter, which furtherreduce the dielectric constant of the SiCOH dielectric material. Thenanometer-sized pores occupy a volume between about 0.5% and about 50%of a volume of the material. When these voids are present, the materialis known as porous SiCOH or “pSiCOH”.

FIG. 3 shows a universal curve of cohesive strength vs. dielectricconstant including prior art dielectrics as shown in FIG. 1 as well asthe inventive SiCOH dielectric material. The plot in FIG. 3 shows thatthe inventive SiCOH dielectric has a higher cohesive strength than priorart dielectrics at equivalent values of k. In FIGS. 1 and 3, the k isreported as the relative dielectric constant.

In a first embodiment of the present invention, a stable ultra low kSiCOH dielectric material is provided that has a dielectric constant of3.0, a tensile stress of 30 MPa or less, an elastic modulus greater than15 GPa, cohesive strength greater than about 6 J/m², a crack developmentvelocity in water of not more than 1×10⁻¹⁰ m/sec for a film thickness of3 microns, and a fraction of the C atoms are bonded in the functionalgroup Si—CH₂—Si, wherein said methylene, CH₂ carbon fraction is about0.1 is provided. Within the invention and as stated above, this fractionmay be between about 0.05 to about 0.5, as measured by C solid stateNMR.

In a second embodiment of the present invention, a stable ultra low kSiCOH dielectric material is provided that has a dielectric constant ofless than 2.5, a tensile stress of from about 30 to about 40 MPa orless, an elastic modulus greater than 5 GPa, a cohesive strength greaterthan about 4 J/m², a crack development velocity in water of not morethan 1×10⁻¹⁰ m/sec for a film thickness of 3 microns, and a fraction ofthe C atoms are bonded in the functional group Si—CH₂—Si wherein themethylene carbon fraction is from about 0.05 to about 0.5, as measuredby C solid state NMR.

In some embodiments of the present invention, there is carbon bonded asSi—CH₃ and also carbon bonded as Si—R—Si, where R can be differentorganic groups. 4.

In some embodiments of the present invention, the inventive dielectricmaterial is characterized has (i) being dense or porous and having acohesive strength in a dry ambient, i.e., the complete absence of water,greater than about 3 J/m² and a dielectric constant less than about 2.5,(ii) being dense or porous and having a cohesive strength greater thanabout 3 J/m² at a water pressure of 1570 Pa at 25° C. and a dielectricconstant less than about 3.2 (50% relative humidity), or (iii) beingdense or porous and having a cohesive strength greater than about 2.1J/m² at a water pressure of 1570 Pa at 25° C. and a dielectric constantless than about 2.5.

The inventive SiCOH dielectric of the present invention has more carbonbonded in organic groups bridging between two Si atoms compared to theSi—CH₃ bonding characteristic of prior art SiCOH and pSiCOH dielectrics.

In some other embodiments of the present invention, there may be C—S,Si—S, and optionally S—S bonding in the inventive SiCOH dielectric.

In addition to the aforementioned properties, the SiCOH dielectricmaterials of the present invention are hydrophobic with a water contactangle of greater than 70°, more preferably greater than 80° and exhibita cohesive strength in shaded regions of FIGS. 2A and 2B.

The inventive SiCOH dielectric materials are typically deposited usingplasma enhanced chemical vapor deposition (PECVD). In addition to PECVD,the present invention also contemplates that the SiCOH dielectricmaterials can be formed utilizing chemical vapor deposition (CVD),high-density plasma (HDP), pulsed PECVD, spin-on application, or otherrelated methods.

In the deposition process, the inventive SiCOH dielectric material isformed by providing at least a first carbosilane or alkoxycarbosilaneprecursor (liquid, gas or vapor) comprising atoms of Si, C, O, and H,and an inert carrier such as He or Ar, into a reactor, preferably thereactor is a PECVD reactor, and then depositing a film derived from saidfirst precursor onto a suitable substrate utilizing conditions that areeffective in forming the SiCOH dielectric material of the presentinvention. The present invention yet further provides for optionally anoxidizing agent such as O₂, N₂O, CO₂ or a combination thereof to the gasmixture, thereby stabilizing the reactants in the reactor and improvingthe properties and uniformity of the dielectric film deposited on thesubstrate. The first precursor may include sulfur or S derivativesthereof as well.

Within the present invention, the first precursor comprises at least oneof the following compounds: 1,3-disilacyclobutane, 1,3-disilapropane,1,5-disilapentane, 1,4-bis-trihydrosilyl benzene, or the methoxy andethoxy substituted derivatives of these compounds. Other examples offirst precursors that can be used in the present invention are cyclicprecursors including, but not limited to:octamethyl-1,5-disiloxane-3,7-disilacyclooctane,1,3,5,7-tetramethyl-1,5-disiloxane-3,7-disilacyclooctane,1,3,5,7-tetramethyl-1,3,5,7-tetrasilacyclooctane,1,3,5-trimethyl-1,3,5-trisilacyclohexane,1,3,5-trimethyl-1,3-disiloxane-5-silacyclohexane, and1,3,5-trimethyl-1-siloxane-3,5-disilacyclohexane. Additionally, thepresent invention contemplates related derivatives of disilacyclooctane,tetrasilacyclooctane, disilacyclohexane, silacyclohexane, and similarcyclic carbosilane precursors.

The structures of the preferred cyclic compounds specifically mentionedherein above are shown to illustrate the types of cyclic compoundscontemplated by the present invention (the illustrated structures thusdo not limit the present invention in any way):

The cyclic compounds mentioned above are preferred in the presentinvention because these precursors have a relatively low boiling point,they are similar to precursors proven to work in manufacturing scalePECVD processes, and they include a combination in one molecule of theSi—CH₂—Si bonding group with at least one Si—O bond in the molecule.

Illustrative examples of some other preferred compounds used in formingthe inventive SiCOH dielectric include:1,1,3,3,-tetrahydrido-1,3-disilacyclobutane;1,1,3,3-tetramethoxy(ethoxy)-1,3-disilacyclobutane;1,3-dimethyl-1,3-dimethoxy-1,3-disilacyclobutane; 1,3-disilacyclobutane;1,3-dimethyl-1,3-dihydrido-1,3-disilylcyclobutane; 1,1,3,3,tetrarmethyl-1,3-disilacyclobutane;1,1,3,3,5,5-hexamethoxy-1,3,5-trisilane;1,1,3,3,5,5-hexahydrido-1,3,5-trisilane;1,1,3,3,5,5-hexamethyl-1,3,5-trisilane;1,1,1,3,3,3-hexamethoxy(ethoxy)-1,3-disilapropane; 1,1,3,3-tetramethoxy-1-methyl-1,3-disilabutane; 1,1,3,3-tetramethoxy-1,3-disilapropane;1,1,1,3,3,3-hexahydrido-1,3-disilapropane;3-(1,1-dimethoxy-1-silaethyl)-1,4,4-trimethoxy-1-methyl-1,4-disilpentane;methoxymethane2-(dimethoxysilamethyl)-1,1,4-trimethoxy-1,4-disilabutane;methoxymethane1,1,4-trimethoxy-1,4-disila-2-(trimethoxysilylmethyl)butane;dimethoxymethane, methoxymethane;1,1,1,5,5,5-hexamethoxy-1,5-disilapentane;1,1,5,5-tetramethoxy-1,5-disilahexane;1,1,5,5-tetramethoxy-1,5-disilapentane;1,1,1,4,4,4-hexamethoxy(ethoxy)-1,4-disilylbutane,1,1,1,4,4,4,-hexahydrido-1,4-disilabutane;1,1,4,4-tetramethoxy(ethoxy)-1,4-dimethyl-1,4-disilabutane;1,4-bis-trimethoxy (ethoxy)silyl benzene; 1,4-bis-dimethoxymethylsilylbenzene; and 1,4-bis-trihydrosilyl benzene. Also the corresponding metasubstituted isomers, such as,1,1,1,4,4,4-hexamethoxy(ethoxy)-1,4-disilabut-2-ene;1,1,1,4,4,4-hexamethoxy(ethoxy)-1,4-disilabut-2-yne;1,1,3,3-tetramethoxy(ethoxy)-1,3-disilolane 1,3-disilolane;1,1,3,3-tetramethyl-1,3-disilolane;1,1,3,3-tetramethoxy(ethoxy)-1,3-disilane;1,3-dimethoxy(ethoxy)-1,3-dimethyl-1,3-disilane; 1,3-disilane;1,3-dimethoxy-1,3-disilane;1,1-dimethoxy(ethoxy)-3,3-dimethyl-1-propyl-3-silabutane; or2-silapropane.

In addition to the above mentioned materials, the present invention alsocontemplates sulfur derivatives thereof.

FIG. 4A shows preferred first precursors that can be used in the presentinvention in forming the SiCOH dielectric material. FIG. 4B is anillustration showing additional CVD carbosilane precursors that can beused in the present invention in forming the SiCOH dielectric-material.The sulfur derivatives of the compounds shown in FIGS. 4A and 4B arealso contemplated herein.

Optionally, a second SiCOH precursor may be added to the reactor, forexample, diethoxymethylsilane, octamethyltetrasiloxane,tetramethyltetrasiloxane, trimethylsilane, or any other commonalkylsilane or alkoxysilane (cyclic or linear) molecule.

Optionally, a precursor containing C—S—C or C—[S]_(n)—C or Si—S—Si, orSi—[S]_(n)—Si bonding may be added to the reactor.

In addition to the first precursor, a second precursor (gas, liquid orvapor) comprising atoms of C, H, and optionally O, F and/or N can beused. Optionally, a third precursor (gas, liquid or gas) comprising Gemay also be used.

The second or third precursor may be a hydrocarbon molecule, asdescribed in U.S. Pat. Nos. 6,147,009, 6,312,793, 6,441,491, 6,437,443,6,541,398, 6,479,110 B2, and 6,497,963, the contents of which areincorporated herein by reference.

The method of the present invention may further comprise the step ofproviding a parallel plate reactor, which has a conductive area of asubstrate chuck between about 85 cm² and about 750 cm², and a gapbetween the substrate and a top electrode between about 1 cm and about12 cm. A high frequency RF power is applied to one of the electrodes ata frequency between about 0.45 MHz and about 200 MHz. Optionally, anadditional RF power of lower frequency than the first RF power can beapplied to one of the electrodes.

The conditions used for the deposition step may vary depending on thedesired final dielectric constant of the SiCOH dielectric material ofthe present invention. Broadly, the conditions used for providing astable dielectric material comprising elements of Si, C, O, H that has adielectric constant of about 3.2 or less, a tensile stress of less than45 MPa, an elastic modulus from about 2 to about 15 GPa, and a hardnessfrom about 0.2 to about 2 GPa include: setting the substrate temperatureat between about 100° C. and about 425° C.; setting the high frequencyRF power density at between about 0.1 W/cm² and about 2.0 W/cm²; settingthe first liquid precursor flow rate at between about 10 mg/min andabout 5000 mg/min, optionally setting the second liquid precursor flowrate at between about 10 mg/min to about 5,000 mg/min; optionallysetting the third liquid precursor flow rate at between about 10 mg/minto about 5000 mg/min; optionally setting the inert carrier gases such asHelium (or/and Argon) flow rate at between about 10 sccm to about 5000sccm; setting the reactor pressure at a pressure between about 1000mTorr and about 10,000 mTorr; and setting the high frequency RF powerbetween about 50 W and about 1000 W. Optionally, an ultra low frequencypower may be added to the plasma between about 20 W and about 400 W.When the conductive area of the substrate chuck is changed by a factorof X, the RF power applied to the substrate chuck is also changed by afactor of X.

When an oxidizing agent is employed in the present invention, it isflowed into the PECVD reactor at a flow rate between about 10 sccm toabout 1000 sccm.

While liquid precursors are used in the above example, it is known inthe art that the organosilicon gas phase precursors (such astrimethylsilane) can also be used for the deposition.

The film resulting from the above processes is called herein the “asdeposited film”.

According to the present invention, the fabrication of the stable SiCOHdielectric materials of the present invention may require a combinationof several steps:

the material is deposited on a substrate in a 1^(st) step, usingdeposition tool parameters in a specific range of values given below inthe process embodiments, forming the as deposited film;

the material is cured or treated using thermal, UV light, electron beamirradiation, chemical energy, or a combination of more than one ofthese, forming the final film having the desired mechanical and otherproperties described herein. For example, after deposition a treatmentof the SiCOH film (using both thermal energy and a second energy source)may be performed to stabilize the film and obtain improved properties.The second energy source may be electromagnetic radiation (UV,microwaves, etc.), charged particles (electron or ion beam) or may bechemical (using atoms of hydrogen, or other reactive gas, formed in aplasma).

In a preferred treatment, the substrate (containing the film depositedaccording to the above process) is placed in a ultraviolet (UV)treatment tool, with a controlled environment (vacuum or ultra pureinert gas with a low O₂ and H₂O concentration). A pulsed or continuousUV source may be used.

Within the invention, the UV treatment tool may be connected to thedeposition tool (“clustered”), or may be a separate tool.

As is known in the art, the two process steps will be conducted withinthe invention in two separate process chambers that may be clustered ona single process tool, or the two chambers may be in separate processtools (“declustered”). For porous SiCOH films, the cure step may involveremoval of a sacrificial hydrocarbon (porogen) component, co-depositedwith the dielectric material. Suitable sacrificial hydrocarboncomponents that can be employed in the present invention include, butare not limited to: the second precursors that are mentioned in U.S.Pat. Nos. 6,147,009, 6,312,793, 6,441,491, 6,437,443, 6,541,398,6,479,110 B2, and 6,497,963, the contents of which are incorporatedherein by reference.

The following are examples illustrating material and processingembodiments of the present invention.

EXAMPLE 1 SiCOH Material A

In this example, an inventive SiCOH dielectric, referred to as SiCOHfilm A, which was made in accordance with the present invention, wascharacterized by the data in FIG. 5 and in Table 1 below. Forcomparison, SiCOH films B and C are “typical” prior art SiCOH films,that have a dielectric constant about 2.7-2.8 are also shown in FIG. 5and Table 1.

Referring to FIG. 5, this figure shows solid-state NMR (nuclear magneticresonance) spectra for the ¹³C nuclei for the film SiCOH film A. Peak 33corresponds to ¹³C for CH₃ methyl groups bonded to Si, and the breadthof peak 33 is due to CH₃ groups in different magnetic environments. Thepeak 32 was assigned to ¹³C in —CH₂— species, bridging between two Siatoms, Si—CH₂—Si. Based on the height of peak 32, the fraction of thetotal C in the film that is C present as methylene bridge groups, —CH₂—was about 0.1. Since peaks 33 and 32 were overlapping, this was anestimate only. The areas have not been measured. Also, in FIG. 5 iscurve 35 measured from SiCOH film B and curve 37 measured from SiCOHfilm C. It was seen that spectra 35 and 37 (NMR spectra) from otherSiCOH films, which are “typical” prior art SiCOH films, contained peak33 assigned to CH₃ groups. The spectra 35 and 37 do not contain peak 32.

Table 1 below summarizes the FTIR (Fourier transform infraredspectroscopy) spectra measured from SiCOH films A, B, and C. The numbersin the table are integrated areas under the FTIR peaks, and the lastcolumn is the ratio of two FTIR peak areas. The ratio (CH₂+CH₃)/SiCH₃was calculated in order to show the enhanced contribution of CH₂ speciesto the FTIR peak area of (CH₂+CH₃) in the inventive SiCOH film A. It wasseen that this ratio was about 0.9 in the inventive SiCOH film A, andwas about 0.6 in a typical SiCOH film such as SiCOH film B or C.Moreover, the SiCOH film A contained more CH₂ species than films B or C.From the NMR analysis, these were assigned to Si—CH₂—Si in the inventiveSiCOH film A.

TABLE 1 (CH₂ + CH₃) Ratio of Si—CH₃ total FTIR (CH₂ + CH₃)/ Film PeakArea Peak Area Si—CH₃ SiCOH film A 1.67 1.48 0.89 SiCOH film B 2.18 1.350.62 SiCOH film C 2.09 1.23 0.59

EXAMPLE 2 First Process Embodiment

A 300 mm or 200 mm substrate was placed in a PECVD reactor on a heatedwafer chuck at 350° C. Temperatures between 300°-425° C. may also beused. Any PECVD deposition reactor may be used within the presentinvention. Gas and liquid precursor flows were then stabilized to reacha pressure in the range from 0.1-10 Torr, and RF radiation was appliedto the reactor showerhead for a time between about 5 to about 500seconds.

Specifically and for the growth of the inventive SiCOH dielectricmaterial A containing enhanced Si—CH₂—Si bridging methylene carbon(described above), the single SiCOH precursor was OMCTS(octamethylcyclotetrasiloxane) set at a flow of 2500 mg/m, an oxygen, O₂flow of 220 sccm, a helium, He gas flow of 2000 sccm, said flows werestabilized to reach a reactor pressure of 5 Torr. The wafer chuck wasset at 350° C., and the high frequency RF power of 400 W at a frequencyof 13.6 MHz was applied to the showerhead, and the low frequency RFpower of 60 W at a frequency of 13.6 MHz was applied to the substrate.The film deposition rate was 2025 Angstrom/min.

EXAMPLE 3 Second Process Embodiment

A 300 mm or 200 mm substrate was placed in a PECVD reactor on a heatedwafer chuck at 300°-425° C. and preferably at 350°-400° C. Any PECVDdeposition reactor may be used within the present invention. Gas andliquid precursor flows were then stabilized to reach a pressure in therange from 0.1-10 Torr, and RF radiation was applied to the reactorshowerhead for a time between about 5 to 500 seconds.

Specifically and for the growth of the inventive SiCOH dielectriccontaining enhanced Si—CH₂—Si bridging methylene carbon (describedabove), the conditions used include:1,1,1,3,3,3-hexamethoxy-1,3-disilapropane, flow of 2500 mg/m, an oxygen,O₂ flow of 220 sccm, a helium, He gas flow of 2000 sccm, said flows werestabilized to reach a reactor pressure of 5 Torr. The wafer chuck wasset at 350° C., and the high frequency RF power of 500 W at a frequencyof 13.6 MHz was applied to the showerhead, and the low frequency RFpower of 160 W at a frequency of 13.6 MHz was applied to the substrate.The film deposition rate was in the range between 10-100Angstrom/second.

As is known in the art, each of the above process parameters may beadjusted within the scope of invention described above. For example,different RF frequencies including, but not limited to, 0.26, 0.35, 0.45MHz, may also be used in the present invention. Also for example, the O₂flow rate may be zero, and alternative oxidizers including N₂O, CO, orCO₂ may be used in place of O₂. Also, in the precursor1,1,1,3,3,3-hexamethoxy-1,3-disilapropane, the methoxy substituentgroups may be replaced by hydrido, methyl or ethoxy groups. Also, theprecursor 1,3-disilabutane (H₃Si—CH₂—Si(H₂)—CH₃) may be used in analternative embodiment, and the flow of O₂ and other gases would beadjusted, as is known in the art.

In still other alternative embodiments, any of the carbosilaneprecursors shown in FIGS. 4A and 4B may be used.

EXAMPLE 4 Third Process Embodiment

A 300 mm or 200 mm substrate was placed in a PECVD reactor on a heatedwafer chuck at 300°-425° C. and preferably at 350°-400° C. Any PECVDdeposition reactor may be used within the present invention. Gas andliquid precursor flows were then stabilized to reach a pressure in therange from 1-10 Torr, and RF radiation was applied to the reactorshowerhead for a time between about 5 to 500 seconds.

For the growth of a SiCOH material with k greater than or equal to 1.8,and having enhanced Si—CH₂—Si bridging methylene carbon, two precursorswere used, specifically 1,3-disilacyclobutane and DEMS(diethoxymethylsilane). Within the invention, any alkoxysilane precursormay be used in place of DEMS, including but not limited to: OMCTS,TMCTS, or dimethyldmethoxysilane. Also, within the invention, thealkoxysilane precursor (used in place of DEMS) may be an organosiliconprecursor with a built-in porogen, and may optionally comprise one ofvinylmethyldiethoxysilane, vinyltriethoxysilane,vinyldimethylethoxysilane, cyclohexenylethyltriethoxysilane,1,1-diethoxy-1-silacyclopent-3-ene, divinyltetramethyldisiloxane,2-(3,4-epoxycyclohexyl)ethyltriethoxysilane,2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, epoxyhexyltriethoxysilane,hexavinyldisiloxane, trivinylmethoxysilane, trivinylethoxysilane,vinylmethylethoxysilane, vinylmethyldiethoxysilane,vinylmethyldimethoxysilane, vinylpentamethyldisiloxane,vinyltetramethyldisiloxane, vinyltriethoxysilane, orvinyltrimethoxysilane.

As is known in the art, gases such as O₂ may be added, and He may bereplaced by gases such as Ar, CO₂, or another noble gas.

The conditions used include a DEMS flow of 2000 mg/m, a1,3-disilacyclobutane flow of 100 to 1000 mg/m, and a He gas flow of1000 sccm, said flows were stabilized to reach a reactor pressure of 6Torr. The wafer chuck was set at 350° C., and the high frequency RFpower of 470 W was applied to the showerhead, and the low frequency RF(LRF) power was 0 W so that no LRF was applied to the substrate. Thefilm deposition rate was about 2,000-4,000 Angstrom/second.

As is known in the art, each of the above process parameters may beadjusted within the scope of invention described above. For example,different RF frequencies including, but not limited to, 0.26, 0.35, 0.45MHz, may also be used in the present invention. Also for example, anoxidizer such as O₂, or alternative oxidizers including N₂O, CO, or CO₂may be used. Specifically, the wafer chuck temperature may be lower, forexample, to 150°-350° C.

While 1,3-disilacyclobutane is the preferred carbosilane to provide anenhanced fraction of Si—CH₂-Si bridging methylene carbon, othercarbosilane or alkoxycarbosilane precursors described above can be used,including but not limited to the precursors shown in FIGS. 4A and 4B.

In alternate embodiments, the conditions are adjusted to produce SiCOHfilms with dielectric constant from 1.8 up to 2.7.

In alternate embodiments, other functional groups may be added asbridging groups between Si and Si, using the selected carbosilaneprecursors, with illustrative examples given here. In order to add the—CH₂—CH₂—CH₂— functional group bridging between Si atoms the selectedcarbosilane precursor may be selected from 1,3-disilolane,1,1,3,3-tetramethoxy(ethoxy)-1,3-disilolane or1,1,3,3-tetramethyl-1,3-disilolane.

In order to add the phenyl functional group bridging between Si atomsthe selected carbosilane precursor may be selected 1,4-bis-trimethoxy(ethoxy)silyl benzene, 1,4-bis-dimethoxymethylsilyl benzene,1,4-bis-trihydrosilyl benzene or related Si containing benzenederivatives.

In order to add the HC═CH functional group bridging between Si atoms,the selected carbosilane precursor may be selected from1,1,1,4,4,4-hexamethoxy(ethoxy)-1,4-disilabut-2-ene or another Sicontaining ethylene derivative.

In order to add the C≡C (triple bond) functional group bridging betweenSi atoms, the selected carbosilane precursor may be1,1,1,4,4,4-hexamethoxy -1,4-disilabut-2-yne, 1,1,1,4,4,4-hexaethoxy-1,4-disilabut-2-yne, or another Si containing acetylene derivative.

In the above examples, the precursors are described having methoxy andethoxy substituent groups, but these may be replaced by hydrido ormethyl groups, and a carbosilane molecule containing a mixture ofmethoxy, ethoxy, hydrido and methyl substituent groups may be usedwithin the invention.

EXAMPLE 5 Fourth Process Embodiment

A 300 mm or 200 mm substrate was placed in a PECVD reactor on a heatedwafer chuck at 300°-425° C. and preferably at 350°-400° C. Any PECVDdeposition reactor may be used within the present invention. Gas andliquid precursor flows were then stabilized to reach a pressure in therange from 0.1-10 Torr, and RF radiation was applied to the reactorshowerhead for a time between about 5 to 500 seconds.

For the growth of a SiCOH material with k greater than or equal to 1.8,and having enhanced Si—CH₂—Si bridging methylene carbon, a singlealkoxycarbosilane precursor was used. The linear precursors shown inFIG. 4A are preferred.

The conditions used include a single precursor flow of 2000 mg/m, and aHe gas flow of 1000 sccm, said flows were stabilized to reach a reactorpressure of 6 Torr. The wafer chuck was set at 350° C., and the highfrequency RF power of 470 W was applied to the showerhead, and the lowfrequency RF (LRF) power was 0 W so that no LRF is applied to thesubstrate. The film deposition rate was about 1,000 to 5,000Angstrom/second.

As is known in the art, each of the above process parameters may beadjusted within the invention. Specifically, the wafer chuck temperaturemay be lower, for example 150°-350° C. As is known in the art, gasessuch as O₂ may be added, and He may be replaced by gases such as Ar,CO₂, or another noble gas.

In alternate embodiments, the conditions are adjusted to produce SiCOHfilms with dielectric constant from 1.8 up to 2.7.

While linear precursors from FIG. 4A are the preferred alkoxycarbosilaneto provide an enhanced fraction of Si—CH₂—Si bridging methylene carbon,any alkoxycarbosilane mentioned above in the detailed description of thepresent invention can be used. Other functional groups may be addedusing the selected carbosilane precursors, with illustrative examplesgiven here. In order to add the —CH₂—CH₂—CH₂— functional group bridgingbetween Si atoms, the selected carbosilane precursor may be selectedfrom 1,3-disilolane, 1,1,3,3-tetramethoxy(ethoxy)-1,3-disilolane or1,1,3,3-tetramethyl-1,3-disilolane.

In order to add the phenyl functional group bridging between Si atoms,the selected carbosilane precursor may be selected 1,4-bis-trimethoxy(ethoxy)silyl benzene, 1,4-bis-dimethoxymethylsilyl benzene,1,4-bis-trihydrosilyl benzene or related Si containing benzenederivatives.

In order to add the HC═CH functional group bridging between Si atoms,the selected carbosilane precursor may be selected from1,1,1,4,4,4-hexamethoxy(ethoxy)-1,4-disilabut-2-ene or another Sicontaining ethylene derivative.

In order to add the C≡C (triple bond) functional group bridging betweenSi atoms the selected carbosilane precursor may be1,1,1,4,4,4-hexamethoxy -1,4-disilabut-2-yne, 1,1,1,4,4,4-hexaethoxy-1,4-disilabut-2-yne, or another Si containing acetylene derivative.

In the above examples, the precursors are described having methoxy andethoxy substituent groups, but these may be replaced by hydrido ormethyl groups, and a carbosilane molecule containing a mixture ofmethoxy, ethoxy, hydrido and methyl substituent groups may be usedwithin the invention.

EXAMPLE 6 Fifth Process Embodiment

A 300 mm or 200 mm substrate was placed in a PECVD reactor on a heatedwafer chuck at 300°-425° C. and preferably at 350°-400 ° C. Any PECVDdeposition reactor may be used within the present invention. Gas andliquid precursor flows were then stabilized to reach a pressure in therange from 1-10 Torr, and RF radiation was applied to the reactorshowerhead for a time between about 5 to 500 seconds.

In this example and for the growth of a porous SiCOH material with kgreater than or equal to 1.8, and having enhanced Si—CH₂—Si bridgingmethylene carbon or other organic functions bridging between two Siatoms, a porogen is added according to methods known in the art. Theporogen may be bicycloheptadiene (BCHD), or other molecules described,for example, in U.S. Pat. Nos. 6,147,009, 6,312,793, 6,441,491,6,437,443, 6,541,398, 6,479,110 B2, and 6,497,963.

For the SiCOH precursor, the linear alkoxysilane precursors shown inFIG. 4A are preferred.

The conditions used include a precursor flow of 100-2000 mg/m, a He gasflow of 10-500 sccm, and a porogen flow of about 50-2000 mg/m, saidflows were stabilized to reach a reactor pressure of 7 Torr. The waferchuck was set at 225° C., and the high frequency RF power of 300 W wasapplied to the showerhead, and the low frequency RF (LRF) power was 0 Wso that no LRF was applied to the substrate. The film deposition ratewas about 1,000 to 5,000 Angstrom/second.

As is known in the art, each of the above process parameters may beadjusted within the invention. For example, the wafer chuck temperaturemay be between 150°-350° C.

While the preferred linear alkoxycarbosilanes of FIG. 4A are useful, anyalkoxycarbosilane as mentioned above may be used within the invention.Also within the invention, two SiCOH precursors may be used, for exampleDEMS and a carbosilane or alkoxycarbosilane described above. As is knownin the art, gases such as O₂, N₂O, or another oxidizer may be added, andHe may be replaced by gases such as Ar, CO₂, or another noble gas.Again, other functional groups, as described in the above examples, canbe used to form a bridging group between two Si atoms.

EXAMPLE 7 Sixth Process Embodiment

A 300 mm or 200 mm substrate was placed in a PECVD reactor on a heatedwafer chuck at 300°-425° C. and preferably at 350°-400° C. Any PECVDdeposition reactor may be used within the present invention. Gas andliquid precursor flows were then stabilized to reach a pressure in therange from 1-10 Torr, and RF radiation was applied to the reactorshowerhead for a time between about 5 to 500 seconds.

Specifically, and for the growth of the inventive SiCOH dielectriccontaining enhanced Si—CH₂—Si bridging methylene carbon (describedabove), the conditions used include selecting the precursoroctamethyl-1,5-disiloxane-3,7-disilacyclooctane, and setting flow ofthis precursor at 2500 mg/m, O₂ flow at 200 sccm, helium gas flow at2000 sccm, wherein said flows were stabilized to reach a reactorpressure of 5 Torr. The wafer chuck was set at 350° C., and the highfrequency RF power of 500 W at a frequency of 13.6 MHz was applied tothe showerhead. The film deposition rate was in the range between 10-100Å/second.

As is known in the art, each of the above process parameters may beadjusted within the scope of this invention. For example, different RFfrequencies including, but not limited to, 0.26, 0.35, 0.45 MHz, mayalso be used in the present invention. Also for example, the O₂ flowrate may be zero, or may be in the range 1 to 500 sccm, and alternativeoxidizers including N₂O, CO, or CO₂ may be used in place of O₂. Also,the flow rate of the carbosilane precursor may be in the range 100-5000mg/m. Also, the RF power may be adjusted to improve the film, with atypical range being 100 to 1000 Watts and the pressure may be in therange 0.1 to 50 Torr.

In still other alternative embodiments, any of3,5,7-tetramethyl-1,5-disiloxane-3,7-disilacyclooctane,1,3,5,7-tetramethyl-1,3,5,7-tetrasilacyclooctane,1,3,5-trimethyl-1,3,5-trisilacyclohexane,1,3,5-trimethyl-1,3-disiloxane-5-silacyclohexane,1,3,5-trimethyl-1-siloxane-3,5-disilacyclohexane as well as derivativesof disilacyclooctane, tetrasilacyclooctane, disilacyclohexane,silacyclohexane, and similar cyclic carbosilane precursors may also beused within the invention.

EXAMPLE 8 Seventh Process Embodiment

A 300 mm or 200 mm substrate was placed in a PECVD reactor on a heatedwafer chuck at 300°-425° C. and preferably at 350°-400 ° C. Any PECVDdeposition reactor may be used within the present invention. Gas andliquid precursor flows were then stabilized to reach a pressure in therange from 1-10 Torr, and RF radiation was applied to the reactorshowerhead for a time between about 5 to 500 seconds.

Specifically, and for the growth of the inventive SiCOH dielectriccontaining enhanced Si—CH₂—Si bridging methylene carbon (describedabove), the conditions used include selecting the precursoroctamethyl-1,5-disiloxane-3,7-disilacyclooctane and a porogen molecule,and setting flow of the cyclic precursor and the porogen within therange from 100 to 5000 mg/m. The porogen may be selected according tomethods known in the art. The porogen may be any of the moleculesdescribed, for example, in U.S. Pat. Nos. 6,147,009, 6,312,793,6,441,491, 6,437,443, 6,541,398, 6,479,110 B2, and 6,497,963.

The O₂ flow was set at 200 sccm, and the helium gas flow was set at 2000sccm. In accordance with the present invention the flows were stabilizedto reach a reactor pressure of 5 Torr. The wafer chuck was set at 350°C., and the high frequency RF power of 500 W at a frequency of 13.6 MHzwas applied to the showerhead. The film deposition rate was in the rangebetween 10-100 Å/second.

As is known in the art, each of the above process parameters may beadjusted within the scope of this invention. For example, different RFfrequencies including, but not limited to, 0.26, 0.35, 0.45 MHz, mayalso be used in the present invention. Also for example, the O₂ flowrate may be zero, or may be in the range 1 to 500 sccm, and alternativeoxidizers including N₂O, CO, or CO₂ may be used in place of O₂. Also,the flow rate of the carbosilane precursor may be in the range 100-5000mg/m. Also, the RF power may be adjusted to improve the film, with atypical range being 100 to 1000 Watts and the pressure may be in therange 0.1 to 50 Torr.

In still other alternative embodiments, any of3,5,7-tetramethyl-1,5-disiloxane-3,7-disilacyclooctane,1,3,5,7-tetramethyl-1,3,5,7-tetrasilacyclooctane,1,3,5-trimethyl-1,3,5-trisilacyclohexane,1,3,5-trimethyl-1,3-disiloxane-5-silacyclohexane,1,3,5-trimethyl-1-siloxane-3,5-disilacyclohexane as well as derivativesof disilacyclooctane, tetrasilacyclooctane, disilacyclohexane,silacyclohexane, and similar cyclic carbosilane precursors may also beused within the invention.

The electronic devices which can include the inventive SiCOH dielectricare shown in FIGS. 6-9. It should be noted that the devices shown inFIGS. 6-9 are merely illustrative examples of the present invention,while an infinite number of other devices may also be formed by thepresent invention novel methods.

In FIG. 6, an electronic device 30 built on a silicon substrate 32 isshown. On top of the silicon substrate 32, an insulating material layer34 is first formed with a first region of metal 36 embedded therein.After a CMP process is conducted on the first region of metal 36, aSiCOH dielectric film 38 of the present invention is deposited on top ofthe first layer of insulating material 34 and the first region of metal36. The first layer of insulating material 34 may be suitably formed ofsilicon oxide, silicon nitride, doped varieties of these materials, orany other suitable insulating materials. The SiCOH dielectric film 38 isthen patterned in a photolithography process followed by etching and aconductor layer 40 is deposited thereon. After a CMP process on thefirst conductor layer 40 is carried out, a second layer of the inventiveSiCOH film 44 is deposited by a plasma enhanced chemical vapordeposition process overlying the first SiCOH dielectric film 38 and thefirst conductor layer 40. The conductor layer 40 may be deposited of ametallic material or a nonmetallic conductive material. For instance, ametallic material of aluminum or copper, or a nonmetallic material ofnitride or polysilicon. The first conductor 40 is in electricalcommunication with the first region of metal 36.

A second region of conductor 50 is then formed after a photolithographicprocess on the SiCOH dielectric film 44 is conducted followed by etchingand then a deposition process for the second conductor material. Thesecond region of conductor 50 may also be deposited of either a metallicmaterial or a nonmetallic material, similar to that used in depositingthe first conductor layer 40. The second region of conductor 50 is inelectrical communication with the first region of conductor 40 and isembedded in the second layer of the SiCOH dielectric film 44. The secondlayer of the SiCOH dielectric film is in intimate contact with the firstlayer of SiCOH dielectric material 38. In this example, the first layerof the SiCOH dielectric film 38 is an intralevel dielectric material,while the second layer of the SiCOH dielectric film 44 is both anintralevel and an interlevel dielectric. Based on the low dielectricconstant of the inventive SiCOH dielectric films, superior insulatingproperty can be achieved by the first insulating layer 38 and the secondinsulating layer 44.

FIG. 7 shows a present invention electronic device 60 similar to that ofelectronic device 30 shown in FIG. 6, but with an additional dielectriccap layer 62 deposited between the first insulating material layer 38and the second insulating material layer 44. The dielectric cap layer 62can be suitably formed of a material such as silicon oxide, siliconnitride, silicon oxynitride, silicon carbide, silicon carbo-nitride(SiCN), silicon carbo-oxide (SiCO), and their hydrogenated compounds.The additional dielectric cap layer 62 functions as a diffusion barrierlayer for preventing diffusion of the first conductor layer 40 into thesecond insulating material layer 44 or into the lower layers, especiallyinto layers 34 and 32.

Another alternate embodiment of the present invention electronic device70 is shown in FIG. 8. In the electronic device 70, two additionaldielectric cap layers 72 and 74 which act as a RIE mask and CMP(chemical mechanical polishing) polish stop layer are used. The firstdielectric cap layer 72 is deposited on top of the first ultra low kinsulating material layer 38 and used as a RIE mask and CMP stop, so thefirst conductor layer 40 and layer 72 are approximately co-planar afterCMP. The function of the second dielectric layer 74 is similar to layer72, however layer 74 is utilized in planarizing the second conductorlayer 50. The polish stop layer 74 can be deposited of a suitabledielectric material such as silicon oxide, silicon nitride, siliconoxynitride, silicon carbide, silicon carbo-oxide (SiCO), and theirhydrogenated compounds. A preferred polish stop layer composition isSiCH or SiCOH for layers 72 or 74. A second dielectric layer can beadded on top of the second SiCOH dielectric film 44 for the samepurposes.

Still another alternate embodiment of the present invention electronicdevice 80 is shown in FIG. 9. In this alternate embodiment, anadditional layer 82 of dielectric material is deposited and thusdividing the second insulating material layer 44 into two separatelayers 84 and 86. The intralevel and interlevel dielectric layer 44formed of the inventive ultra low k material is therefore divided intoan interlayer dielectric layer 84 and an intralevel dielectric layer 86at the boundary between via 92 and interconnect 94. An additionaldiffusion barrier layer 96 is further deposited on top of the upperdielectric layer 74. The additional benefit provided by this alternateembodiment electronic structure 80 is that dielectric layer 82 acts asan RIE etch stop providing superior interconnect depth control. Thus,the composition of layer 82 is selected to provide etch selectivity withrespect to layer 86.

Still other alternate embodiments may include an electronic structurewhich has layers of insulating material as intralevel or interleveldielectrics in a wiring structure that includes a pre-processedsemiconducting substrate which has a first region of metal embedded in afirst layer of insulating material, a first region of conductor embeddedin a second layer of the insulating material wherein the second layer ofinsulating material is in intimate contact with the first layer ofinsulating material, and the first region of conductor is in electricalcommunication with the first region of metal, a second region ofconductor in electrical communication with the first region of conductorand is embedded in a third layer of insulating material, wherein thethird layer of insulating material is in intimate contact with thesecond layer of insulating material, a first dielectric cap layerbetween the second layer of insulating material and the third layer ofinsulating material and a second dielectric cap layer on top of thethird layer of insulating material, wherein the first and the seconddielectric cap layers are formed of a material that includes atoms ofSi, C, O and H, or preferably a SiCOH dielectric film of the presentinvention.

Still other alternate embodiments of the present invention include anelectronic structure which has layers of insulating material asintralevel or interlevel dielectrics in a wiring structure that includesa pre-processed semiconducting substrate that has a first region ofmetal embedded in a first layer of insulating material, a first regionof conductor embedded in a second layer of insulating material which isin intimate contact with the first layer of insulating material, thefirst region of conductor is in electrical communication with the firstregion of metal, a second region of conductor that is in electricalcommunication with the first region of conductor and is embedded in athird layer of insulating material, the third layer of insulatingmaterial is in intimate contact with the second layer of insulatingmaterial, and a diffusion barrier layer formed of the dielectric film ofthe present invention deposited on at least one of the second and thirdlayers of insulating material.

Still other alternate embodiments include an electronic structure whichhas layers of insulating material as intralevel or interleveldielectrics in a wiring structure that includes a pre-processedsemiconducting substrate that has a first region of metal embedded in afirst layer of insulating material, a first region of conductor embeddedin a second layer of insulating material which is in intimate contactwith the first layer of insulating material, the first region ofconductor is in electrical communication with the first region of metal,a second region of conductor in electrical communication with the firstregion of conductor and is embedded in a third layer of insulatingmaterial, the third layer of insulating material is in intimate contactwith the second layer of insulating material, a reactive ion etching(RIE) hard mask/polish stop layer on top of the second layer ofinsulating material, and a diffusion barrier layer on top of the RIEhard mask/polish stop layer, wherein the RIE hard mask/polish stop layerand the diffusion barrier layer are formed of the SiCOH dielectric filmof the present invention.

Still other alternate embodiments include an electronic structure whichhas layers of insulating materials as intralevel or interleveldielectrics in a wiring structure that includes a pre-processedsemiconducting substrate that has a first region of metal embedded in afirst layer of insulating material, a first region of conductor embeddedin a second layer of insulating material which is in intimate contactwith the first layer of insulating material, the first region ofconductor is in electrical communication with the first region of metal,a second region of conductor in electrical communication with the firstregion of conductor and is embedded in a third layer of insulatingmaterial, the third layer of insulating material is in intimate contactwith the second layer of insulating material, a first RIE hard mask,polish stop layer on top of the second layer of insulating material, afirst diffusion barrier layer on top of the first RIE hard mask/polishstop layer, a second RIE hard mask/polish stop layer on top of the thirdlayer of insulating material, and a second diffusion barrier layer ontop of the second RIE hard mask/polish stop layer, wherein the RIE hardmask/polish stop layers and the diffusion barrier layers are formed ofthe SiCOH dielectric film of the present invention.

Still other alternate embodiments of the present invention includes anelectronic structure that has layers of insulating material asintralevel or interlevel dielectrics in a wiring structure similar tothat described immediately above but further includes a dielectric caplayer which is formed of the SiCOH dielectric material of the presentinvention situated between an interlevel dielectric layer and anintralevel dielectric layer.

In some embodiments as shown, for example in FIG. 10, an electronicstructure containing at least two metallic conductor elements (labeledas reference numerals 97 and 101) and a SiCOH dielectric material(labeled as reference numeral 98). Optionally, metal contacts 95 and 102are used to make electrical contact to conductors 97 and 101. Theinventive SiCOH dielectric 98 provides electrical isolation and lowcapacitance between the two conductors. The electronic structure is madeusing a conventional technique that is well known to those skilled inthe art such as described, for example, in U.S. Pat. No. 6,737,727, theentire content of which is incorporated herein by reference.

The at least two metal conductor elements are patterned in a shaperequired for a function of a passive or active circuit elementincluding, for example, an inductor, a resistor, a capacitor, or aresonator.

Additionally, the inventive SiCOH can be used in an electronic sensingstructure wherein the optoelectronic sensing element (detector) shown inFIG. 11A or 11B is surrounded by a layer of the inventive SiCOHdielectric material. The electronic structure is made using aconventional technique that is well known to those skilled in the art.Referring to FIG. 1A, a p-i-n diode structure is shown which can be ahigh speed Si based photodetector for IR signals. The n+ substrate is110, and atop this is an intrinsic semiconductor region 112, and withinregion 112 p+ regions 114 are formed, completing the p-i-n layersequence. Layer 116 is a dielectric (such as SiO₂) used to isolate themetal contacts 118 from the substrate. Contacts 118 provide electricalconnection to the p+ regions. The entire structure is covered by theinventive SiCOH dielectric material, 120. This material is transparentin the IR region, and serves as a passivation layer.

A second optical sensing structure is shown in FIG. 11B, this is asimple p-n junction photodiode, which can be a high speed IR lightdetector. Referring to FIG. 11B, the metal contact to substrate is 122,and atop this is an n-type semiconductor region 124, and within thisregion p+ regions 126 are formed, completing the p-n junction structure.Layer 128 is a dielectric (such as SiO₂) used to isolate the metalcontacts 130 from the substrate. Contacts 130 provide electricalconnection to the p+ regions. The entire structure is covered by theinventive SiCOH dielectric material, 132. This material is transparentin the IR region, and serves as a passivation layer.

While the present invention has been described in an illustrativemanner, it should be understood that the terminology used is intended tobe in a nature of words of description rather than of limitation.Furthermore, while the present invention has been described in terms ofa preferred and several alternate embodiments, it is to be appreciatedthat those skilled in the art will readily apply these teachings toother possible variations of the invention.

1. A method of fabricating a SiCOH dielectric material comprising:placing a substrate into a plasma enhanced chemical vapor depositionreactor; providing octamethyl-1,5-disiloxane-3,7-disilacyclooctane as acyclic carbosilane precursor, a porogen, oxygen and helium to saidreactor; depositing via plasma enhanced chemical vapor deposition adielectric film derived from said cyclic carbosilane precursor onto saidsubstrate, said plasma enhanced chemical vapor deposition includes areactor pressure of 5 Torr, a flow of said cyclic carbosilane precursorand said porogen from 100 to 5000 mg/m, an O₂ flow of 200 sccm, a heliumflow of 2000 sccm, and applying an RF power of 500 W at a frequency of13.6 to a showerhead of said reactor, wherein said dielectric film has adielectric constant of 3.2 or less, at least atoms of Si, C, O, H and acovalently bonded tri-dimensional network structure in which some of theC atoms within said network structure are bonded as Si—CH₃ functionalgroups, and some of the C atoms in said network structure are bonded asSi—CH₂ —Si; and treating said deposited dielectric film using acombination of thermal energy and UV light energy.